The only red dot that I can recommend is the Leupold/Gilmore Red dot. I have tried the Tasco Accudot but my SBH shook it apart. As far as sizes go that will boil down to personal preference, I find that the larger scopes are much better suited to quick shooting, rather than high accuracy, due to the fact that it seems to me that the dot is harder to center, as well, in the larger sights as it is in the smaller tubes.

Gordon